1. Field of the Invention
This invention deals with vehicles for transporting and dispensing solid materials such as fertilizers or the like over the ground, and deals more particularly with a hydraulic system driven by one of the vehicle's ground engaging wheels for independently driving and controlling the operation of a pair of material handling and dispensing mechanisms at different rates of speed.
2. Description of the Prior Art
One common form of a solid material dispensing vehicle adapted to be towed by a towing vehicle includes a material hopper provided with a conveyor belt therebeneath for carrying material to a discharge area where a rotating spreader fan scatters the material over the ground as the vehicle travels over the ground. The conveyor is normally powered by means of a mechanical drive train connected with one of the vehicle's ground engaging wheels which results in conveyor movement that is directly proportional to the rotational speed of the driving wheel and is therefore also directly proportional to the vehicle's speed over the ground. A proportional relationship between conveyor movement and the vehicle's speed results in dispensing material from the vehicle at a rate of application which is constant regardless of variation of the vehicle's speed. The specific rate of material dispensing is determined by the selection of particular gear ratios in the drive train and is further determined by the position of a manually adjustable gate structure adjacent the discharge area which varies the size of a discharge opening in the latter, thereby determining the rate at which the conveyor dispenses material through the discharge opening.
Normally, it is desirable to maintain the spreader fan at a constant rotational speed in order to dispense the material in a uniform pattern across a constant width of the ground, regardless of the vehicle's speed. In the past, any of several approaches have been taken to provide constant rotational speed of the spreader fan: a power takeoff shaft or other constant speed power shaft driven by the towing vehicle may be connected to the dispensing vehicle in order to provide a constant drive speed to the spreader fan; a constant speed gasoline engine may be mounted directly on the dispensing vehicle, or the towing vehicle may be adapted to provide a source of constant flow hydraulic power which is hydraulically coupled to the dispensing vehicle, and more particularly to a hydraulic motor for driving the spreader fan at a constant speed. A less desirable approach to the problem involves driving the spreader fan by means of a mechanical drive train connected to one of the vehicle's ground engaging wheels; however, this driving configuration requires that the dispensing vehicle be towed at a single, specific speed in order to accomplish proper rotational speed of the spreader fan.
From the foregoing, it is apparent that separate sources of power have previously been needed to drive the conveyor and spreader fan at different respective rates, and in most cases a drive train coupling was required between the dispensing vehicle and the towing vehicle while considerable gear mechanism was needed to obtain the desired drive ratios. Thus, there is a need in the art for a single, self-contained, power and control system for driving both the conveyor and spreader fan at different respective rates of speed which eliminates the need for separate power drive mechanisms associated with the conveyor and spreader fan, and further eliminates the need for a drive train coupling between the towing vehicle and dispensing vehicle.